Food prices in America rose 3.9% in February, the largest monthly gain in 36 years, The Labor Department reported yesterday. It marked the largest increase since a 4.2% climb in November 1974. Most of the increase was due to a huge spike in vegetable prices because of freezing weather in Florida, California, Texas and Mexico. Prices doubled in a matter of weeks on many wholesale vegetables. In the year ahead, expect to see the largest food price increases in the protein group: chicken, beef, and pork, as well as dairy items. One key reason – the price of corn, used as feed by ranchers and farmers, has doubled in the past year. But vegetarians won’t get off easy – produce and orange juice are rising sharply, as well. The U.S. Department of Agriculture expects the average price of food in 2011 to be 4% higher than last year. Some private forecasters say that, by December, prices could be as much as 6% higher than in December 2010.